The present invention relates to a burglarproof device for a hydraulic machine, and more particularly to a burglarproof device for hydraulic machines including construction machines such as hydraulic excavators.
Prior art burglarproof devices for hydraulic machines are disclosed in JP, A, 2-132233 and JP, A, 63-116958, for example. These burglarproof devices are designed to release start-up prevention means for an engine start-up system from an actuated state only when ten numeral keys of a 10-key input unit are depressed in the order of the password predetermined, allowing the machine to operate while any other person who does not know the password is prohibited from operating the machine. The hydraulic machine is thereby secured against burglary. Further, FIG. 1 of JP, U, 4-70559 illustrates a device constructed in a similar manner as in the above prior art for the purpose of protecting mechanics against the event that any other person may unknowingly start up the machine under service work. This prior art also has a function common to the burglar proof device in prohibiting any other person from operating the machine. In addition, FIG. 2 of JP, U, 4-70559 proposes an arrangement adapted to cut off not an engine start-up system, but an engine fuel system for the same purpose.